Downlink 8 TX codebook sub-sampling for CSI feedback

ABSTRACT

This invention is codebook sub-sampling of the reporting of RI, CQI, W 1  and W 2 . If CSI mode  1  is selected RI and W 1  are jointly encoded using codebook sub-sampling in report  1 . If CSI mode  2  is selected W 1  and W 2  are jointly encoded using codebook sub-sampling in report  2.

CLAIM OF PRIORITY

This application claims priority under 35 U.S.C. 119(e)(1) to U.S.Provisional Application No. 61/379,525 filed Sep. 2, 2010, U.S.Provisional Application No. 61/384,925 filed Sep. 21, 2010 and U.S.Provisional Application No. 61/385,671 filed Sep. 23, 2010.

TECHNICAL FIELD OF THE INVENTION

The technical field of this invention is wireless communication such aswireless telephony.

BACKGROUND OF THE INVENTION

This invention deals with the problem of signaling channel stateinformation (CSI) between a user equipment (UE) and a base station(eNB).

SUMMARY OF THE INVENTION

This invention is codebook sub-sampling of the reporting of RankIndicator (RI), Channel Quality Indicator (CQI), first precoding matrix(W1) and second precoding matrix (W2). If CSI mode 1 is selected RI andW1 are jointly encoded using codebook sub-sampling in report 1. If CSImode 2 is selected W1 and W1 are jointly encoded using codebooksub-sampling in report 2.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of this invention are illustrated in thedrawings, in which:

FIG. 1 illustrates an exemplary prior art wireless communication systemto which this application is applicable;

FIG. 2 shows the Evolved Universal Terrestrial Radio Access (E-UTRA)Time Division Duplex (TDD) frame structure of the prior art;

FIG. 3 illustrates the process of RI, CQI W1 and W2 reporting accordingto this invention; and

FIG. 4 is a block diagram illustrating internal details of a basestation and a mobile user equipment in the network system of FIG. 1suitable for implementing this invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows an exemplary wireless telecommunications network 100. Theillustrative telecommunications network includes base stations 101, 102and 103, though in operation, a telecommunications network necessarilyincludes many more base stations. Each of base stations 101, 102 and 103(eNB) are operable over corresponding coverage areas 104, 105 and 106.Each base station's coverage area is further divided into cells. In theillustrated network, each base station's coverage area is divided intothree cells. Handset or other user equipment (UE) 109 is shown in Cell A108. Cell A 108 is within coverage area 104 of base station 101. Basestation 101 transmits to and receives transmissions from UE 109. As UE109 moves out of Cell A 108 and into Cell B 107, UE 109 may be handedover to base station 102. Because UE 109 is synchronized with basestation 101, UE 109 can employ non-synchronized random access toinitiate handover to base station 102.

Non-synchronized UE 109 also employs non-synchronous random access torequest allocation of up-link 111 time or frequency or code resources.If UE 109 has data ready for transmission, which may be traffic data,measurements report, tracking area update, UE 109 can transmit a randomaccess signal on up-link 111. The random access signal notifies basestation 101 that UE 109 requires up-link resources to transmit the UEsdata. Base station 101 responds by transmitting to UE 109 via down-link110, a message containing the parameters of the resources allocated forUE 109 up-link transmission along with a possible timing errorcorrection. After receiving the resource allocation and a possibletiming advance message transmitted on down-link 110 by base station 101,UE 109 optionally adjusts its transmit timing and transmits the data onup-link 111 employing the allotted resources during the prescribed timeinterval.

Base station 101 configures UE 109 for periodic uplink soundingreference signal (SRS) transmission. Base station 101 estimates uplinkchannel quality information (CSI) from the SRS transmission.

FIG. 2 shows the Evolved Universal Terrestrial Radio Access (E-UTRA)time division duplex (TDD) Frame Structure. Different sub-frames areallocated for downlink (DL) or uplink (UL) transmissions. Table 1 showsapplicable DL/UL subframe allocations. D refers to a downlink sub-frame,U refers to an uplink sub-frame, S refers to a special sub-frame forswitching between downlink to uplink.

TABLE 1 Configu- Switch-point Sub-frame number ration periodicity 0 1 23 4 5 6 7 8 9 0 5 ms D S U U U D S U U U 1 5 ms D S U U D D S U U D 2 5ms D S U D D D S U D D 3 10 ms D S U U U D D D D D 4 10 ms D S U U D D DD D D 5 10 ms D S U D D D D D D D 6 10 ms D S U U U D S U U D

CSI (channel state information) feedback from UE to eNB consists of rankindicator (RI), precoding matrix indicator (PMI) and channel qualityindicator (CQI). RI denotes the number of layers in data transmissionrecommended by the UE. PMI is the index to the recommended precodingmatrix for data transmission, derived from a codebook. CQI is thechannel quality when the reported RI/PMI are used for data transmission.

The 8 TX codebook for Rel. 10 downlink (DL) MIMO was adopted in theapplicable standard for 8 antenna ports system. For 8 TX each precodingmatrix is a multiplication of two component matrices denoted by W=W1*W2.The component codebook for W1 and W2 are denoted respectively C1 and C2.For CSI feedback, both W1 and W2 need to be reported. Because PhysicalUplink Shared CHannel (PUCCH) payload is limited (maximum 11-bits), notall precoding matrices in the C1 and C2 codebook can be used in PUCCHfeedback. Following the agreement on CSI reporting modes for PUCCH, thepossibility of applying codebook sub-sampling needs to be investigated.This document outlines some possible codebook sub-sampling mechanisms inrelation to PUCCH mode 1-1 for both CSI mode 1 and 2. This facilitatesfurther comparison between CSI mode 1 and 2. The adopted reportingstructure is given in Table 2. Table 2 shows the reporting structure forPUCCH mode 1-1. The notation x+y (as in RI+W1, W1+W2 indicates thepossibility for joint encoding. Similarly the notation x/y (as in RI/WI,W1/W2 indicates the possibility for joint encoding.

TABLE 2 CSI mode 1 CSI mode 2 Report 1 RI + W1 RI Report 2 CQI, W2 CQI,W1 + W2From Table 2 it is apparent that in CSI mode 1 report 2 simply followsthe Rel. 8 Precoding Matrix Indicator (PMI) principle where W2 isanalogous to the Rel. 8 PMI. In CSI mode 2 report carries only the Rel.8 RI making codebook sub-sampling irrelevant. Codebook sub-sampling isneeded for CSI mode 1 report 1 and CSI mode 2 report 2. This will bediscussed below.

FIG. 3 illustrates this process. FIG. 3 begins with start block 301.Test block 302 determines if CSI mode 1 or CSI mode 2 is selected. IfCSI mode 1 is selected, then block 303 generates report 1. RI and W1 arejointly encoded. They are also codebook sub-sampled according to one ofTables 3 to 15 below. Block 304 generates report 2 with CQI and W2separately encoded.

If CSI mode 2 is selected, then block 305 generates report 1. Thisincludes the separately encoded RI. Block 306 generates report 2 withCQI, W1 and W2. W1 and W2 are jointly encoded with codebook sub-samplingaccording to one of Tables 16 to 19. FIG. 3 ends with continue block306.

For CSI report on PUSCH, codebook sub-sampling may be performed on W2 asshown in Tables 21 to 25.

Codebook Sub-Sampling

Codebook sub-sampling is selected for the two scenarios mentioned above.

CSI Mode 1 Report 1 (RI+W1)

In this case, the total payload RI+W1 is kept within 5 bits to ensurethat the effect of error propagation is not significant for anypractical range of RI reporting interval. The following actions areperformed to attain such goal when sub-sampling is performed on thecodebook C1 for W1. First, joint encoding of RI and W1 follow thestandard. This ensures efficient signaling of W1 with minimum overhead.Second, overlapping beams between two different W1 matrices can beskipped whenever appropriate as overlapping beam can be seen as anoptimization feature. Third, since precoding gain is expected to besmall for higher-rank transmission (rank>4), fixed precoding using onlyone W1 matrix may be appropriate.

Tables 3 to 15 show three exemplary W1 codebook sub-sampling schemes.These examples are ordered in increasing total number of hypotheses. Itis possible to combine a part of one example with other parts from otherexamples. For example, for RI=1 to 4 example 1 may be used while forRI=5 to 8 example 3 may be used. While the total number of hypothesesdiffers, all these exemplary designs occupy a maximum of 5 bits forjointly coded RI and W1. Thus some additional encoding may be performedto reap the advantage of the design with the smallest number ofhypotheses. For instance, example 1 can use an encoding technique to map24 hypotheses onto 2⁵=32 available code points. Otherwise, it seems moreattractive to choose example 3 as the 5-bit payload carries moreprecoding hypotheses.

Table 3 shows a first example of sub-sampling of codebook C1 with 5-bitRI+W1.

TABLE 3 No. W1 RI Chosen W1 index for sub-sampling (i₁) hypotheses 1 0,2, 4, 6, 8, 10, 12, 14 (no overlap) 8 2 0, 2, 4, 6, 8, 10, 12, 14 (nooverlap) 8 3 0, 2 (no overlap) 2 4 0, 2 (no overlap) 2 5 0 (fixedprecoding) 1 6 0 (fixed precoding) 1 7 0 (fixed precoding) 1 8 0 1 Totalno. hypotheses across ranks, 24, 5 bits required coding bits

Table 4 shows a second example of sub-sampling of codebook C1 with 5-bitRI+W1.

TABLE 4 No. W1 RI Chosen W1 index for sub-sampling (i₁) hypotheses 1 0,2, 4, 6, 8, 10, 12, 14 (no overlap) 8 2 0, 2, 4, 6, 8, 10, 12, 14 (nooverlap) 8 3 0, 1, 2, 3 (all) 4 4 0, 1, 2, 3 (all) 4 5 0 (fixedprecoding) 1 6 0 (fixed precoding) 1 7 0 (fixed precoding) 1 8 0 1 Totalno. hypotheses across ranks, 28, 5 bits required coding bits

Table 5 shows a third example of sub-sampling of codebook C1 with 5-bitRI+W1.

TABLE 5 No. W1 RI Chosen W1 index for sub-sampling (i₁) hypotheses 1 0,2, 4, 6, 8, 10, 12, 14 (no overlap) 8 2 0, 2, 4, 6, 8, 10, 12, 14 (nooverlap) 8 3 0, 1, 2, 3 (all) 4 4 0, 1, 2, 3 (all) 4 5 0, 1 (use 2 outof 4) 2 6 0, 1 (use 2 out of 4) 2 7 0, 1 (use 2 out of 4) 2 8 0 1 Totalno. hypotheses across ranks, 31, 5 bits required coding bits

Table 6 shows a fourth example of sub-sampling of codebook C1 with 5-bitRI+W1.

TABLE 6 No. W1 RI Chosen W1 index for sub-sampling (i₁) hypotheses 1 0,2, 4, 6, 8, 10, 12, 14 (no overlap) 8 2 0-15 16 3 0, 2 (no overlap) 2 40, 2 (no overlap) 2 5 0 (fixed precoding) 1 6 0 (fixed precoding) 1 7 0(fixed precoding) 1 8 0 1 Total no. hypotheses across ranks, 32, 5 bitsrequired coding bits

Table 7 shows a fifth example of sub-sampling of codebook C1 with 5-bitRI+W1.

TABLE 7 No. W1 RI Chosen W1 index for sub-sampling (i₁) hypotheses 10-15 16 2 0, 2, 4, 6, 8, 10, 12, 14 (no 8 overlap) 3 0, 2 (no overlap) 24 0, 2 (no overlap) 2 5 0 (fixed precoding) 1 6 0 (fixed precoding) 1 70 (fixed precoding) 1 8 0 1 Total no. hypotheses across ranks, 32, 5bits required coding bits

As an alternative, it is possible for the RI/W1 payload to beUE-specific. Thus the RI/W1 payload varies as a function of the UEcategory, such as a maximum number of layers supported in downlink datatransmission in PDSCH or number of UE receive antennas. For example, ifa UE has only two receive antennas or can receive up to 2 layers indownlink data transmission, RI+W1 reporting is limited to RI=1 or RI=2.Hence in Tables 3-7 the payload of RI/W1 is determined by the totalentries in RI=1 and RI=2. This is already supported in Rel. 8 where theRI bit width can be 1 or 2 bits based on UE category. Thus the payloadof RI/W1 may be reduced to 4 bits or sub-sampling may not be performedfor 2 Rx and 4 Rx UE with 5-bits RI/W1. Tables 8 to 14 show a number ofexemplary sub-sampling cases.

Table 8 shows a sub-sampling of codebook C1 for 4-bit RI+W1 for a2-layer capable UE (2 RX).

TABLE 8 No. W1 RI Chosen W1 index for sub-sampling (i₁) hypotheses 1 0,2, 4, 6, 8, 10, 12, 14 (no overlap) 8 2 0, 2, 4, 6, 8, 10, 12, 14 (nooverlap) 8 Total no. hypotheses across ranks, 16, 4 bits required codingbits

Table 9 shows sub-sampling of codebook C1 for 5-bit RI+W1 for a 2-layercapable UE (2 RX) with no sub-sampling.

TABLE 9 No. W1 RI Chosen W1 index for sub-sampling (i₁) hypotheses 10-15 16 2 0-15 16 Total no. hypotheses across ranks, 32, 5 bits requiredcoding bits

Table 10 shows sub-sampling of codebook C1 for 5-bit RI+W1 for 2-layercapable UE (2 RX).

TABLE 10 No. W1 RI Chosen W1 index for sub-sampling (i₁) hypotheses 1 0,2, 4, 6, 8, 10, 12, 14 (no overlap) 8 2 0-15 16 Total no. hypothesesacross ranks, 24, 5 bits required coding bits

Table 11 shows sub-sampling of codebook C1 for 5-bit RI+W1 for 2-layercapable UE (2 RX).

TABLE 11 No. W1 RI Chosen W1 index for sub-sampling (i₁) hypotheses 10-15 16 2 0, 2, 4, 6, 8, 10, 12, 14 (no overlap) 8 Total no. hypothesesacross ranks, 24, 5 bits required coding bits

Table 12 shows sub-sampling of codebook C1 5-bit RI+W1 for 4-layercapable UE (4 RX).

TABLE 12 No. W1 RI Chosen W1 index for sub-sampling (i₁) hypotheses 1 0,2, 4, 6, 8, 10, 12, 14 (no overlap) 8 2 0-15 16 3 0-3 4 4 0-3 4 Totalno. hypotheses across ranks, 32, 5 bits required coding bits

Table 13 shows sub-sampling of codebook C1 with 5-bit RI+W1 for 4-layercapable UE (4 RX).

TABLE 13 No. W1 RI Chosen W1 index for sub-sampling (i₁) hypotheses 10-15 16 2 0, 2, 4, 6, 8, 10, 12, 14 (no 8 overlap) 3 0-3 4 4 0-3 4 Totalno. hypotheses across ranks, 32, 5 bits required coding bits

Table 14 shows sub-sampling of codebook C for 5-bit RI+W1 for 4-layercapable UE (4 RX).

TABLE 14 No. W1 RI Chosen W1 index for sub-sampling (i₁) hypotheses 1 0,2, 4, 6, 8, 10, 12, 14 (no overlap) 8 2 0, 2, 4, 6, 8, 10, 12, 14 (nooverlap) 8 3 0-3 4 4 0-3 4 Total no. hypotheses across ranks, 24, 5 bitsrequired coding bits

The maximum payload associated with RI depends on the UE capability ofthe maximum number of layers. The codebook sub-sampling scheme for agiven rank or across the ranks can be designed so that it is notdependent on the UE capability in terms of the maximum number of layers.Table 15 shows an example. For ranks 5 to 7, it is possible to utilizeonly one 1 of 4 available W1 matrices if fixed precoding is desired.This nets to a total of 24 hypotheses. This can be done if reducing thetotal number of hypotheses from 27 to 24 is beneficial despite the samepayload of 5 bits. Such a scenario is possible if the reserved (unused)hypotheses can be used for other purposes. In addition the use of someadditional channel coding is applied on top of the (20,N) Reed-Mullercode to improve error protection.

Table 15 shows an example codebook sub-sampling scheme for CSI mode 1report 1.

TABLE 15 No. W1 R1 Chosen W1 index for sub-sampling (i₁) hypotheses 1 0,2, 4, 6, 8, 10, 12, 14 (no 8 overlapping beams) 2 0, 2, 4, 6, 8, 10, 12,14 (no 8 overlapping beams) 3 0, 2 (no overlapping beams) 2 4 0, 2 (nooverlapping beams) 2 5 0, 1 (use 2 out of 4) 2 6 0, 1 (use 2 out of 4) 27 0, 1 (use 2 out of 4) 2 8 0 1 Total no. W1 + RI hypotheses across 16,4 bits ranks 1-2 (max. layers = 2), required coding bits Total no. W1 +RI hypotheses across 20, 4 bits ranks 1-4 (max. layers = 4), requiredcoding bits Total no. W1 + RI hypotheses across 27, 5 bits ranks 1-8(max. layers = 8), required coding bitsCSI Mode 2 Report 2 (CQI, W1+W2)

In this case, the total payload of CQI together with W1+W2 should notexceed 11 bits to ensure the same worst-case coverage as the Rel. 8format 2/2a/2b. Hence, the following actions are performed to attainsuch goal when sub-sampling is performed on the codebook C1+C2 forW1+W2:

To maintain the maximum overhead of 11 bits:

RI=1: Since CQI occupies 4 bits, the payload for W1+W2 should not exceed7 bits

RI>1: Since CQI occupies 7 bits, the payload for W1+W2 should not exceed4 bits

Joint encoding of W1 and W2 should be performed whenever possible: Thisensures efficient signaling of W1+W2 with minimum overhead.

Overlapping beams between two different W1 matrices can be skippedwhenever appropriate as overlapping beam can be seen as an optimizationfeature.

Since precoding gain is expected to be small for higher-ranktransmission (rank>4), fixed precoding (using only one W1 matrix) shouldalso be considered whenever appropriate.

Sub-sampling of C1 and C2 can also be performed jointly rather thanseparately.

Keeping the above principles in mind, three exemplary W1+W2 codebooksub-sampling schemes are given below in Tables 16 to 19.

Table 16 shows a first example of sub-sampling of codebook C1+C2.

FIG. 16 No. W1 + W2 RI Chosen W1 + W2 index for sub-sampling hypotheses1 W1: 0, 2, 4, 6, 8, 10, 12, 14 (no overlap) 8 × 8 = 64, (i₁) 6 bits W2:for each W1, choose only Y = e1 and e3 with all 4 possible co-phasing[note: this resembles (N, Nb) = (16, 1) design] (i₂ = 0-3, 8-11) 2 W1:0, 2, 4, 6, 8, 10, 12, 14 (no overlap) 8 × 2 = 18, (i₁) 4 bits W2: foreach W1, choose only (Y1, Y2) = (e1, e1) with all 2 possible co-phasing[note: this resembles (N, Nb) = (8, 1) design] (i₂ = 0-1) 3 W1: 0, 2 (nooverlap) (i₁) 2 × 8 = 16, W2: for each W1, choose only 8 out of 16 4bits possible (Y1, Y2), e.g. the even indexed or the last 8 (i₂ = 0, 2,... 14 or 8-15) 4 W1: 0, 2 (no overlap) (i₁) 2 × 8 = 16 W2: all 4 bits 5W1: 0 (fixed precoding) (i₁) 1, 0 bit 6 W1: 0 (fixed precoding) (i₁) 1,0 bit 7 W1: 0 (fixed precoding) (i₁) 1, 0 bit 8 W1: 0 (i₁) 1, 0 bit

Table 17 shows a second example sub-sampling of codebook C1+C2.

TABLE 17 No. W1 + W2 RI Chosen W1 + W2 index for sub-sampling hypotheses1 W1: all (i₁) 16 × 4 = 64, W2: for each W1, choose only Y = e1 with all4 6 bits possible co-phasing [note: this resembles (N, Nb) = (16, 1)design] (i₂ = 0-3) 2 W1: 0, 2, 4, 6, 8, 10, 12, 14 (no overlap) 8 × 2 =18, (i₁) 4 bits W2: for each W1, choose only (Y1, Y2) = (e1, e1) withall 2 possible co-phasing [note: this resembles (N, Nb) = (8, 1) design](i₂ = 0-1) 3 W1: 0, 2 (no overlap) (i₁) 2 × 8 = 16, W2: for each W1,choose only 8 out of 16 4 bits possible (Y1, Y2), e.g. the even indexedor the last 8 (i₂ = 0, 2, . . . 14 or 8-15) 4 W1: 0, 2 (no overlap) (i₁)2 × 8 = 16, W2: all 4 bits 5 W1: 0 (fixed precoding) (i₁) 1, 0 bit 6 W1:0 (fixed precoding) (i₁) 1, 0 bit 7 W1: 0 (fixed precoding) (i₁) 1, 0bit 8 W1: 0 (i₁) 1, 0 bit

Table 18 shows a third example of sub-sampling of codebook C1+C2.

TABLE 18 No. W1 + W2 RI Chosen W1 + W2 index for sub-sampling hypotheses1 W1: 0, 2, 4, 6, 8, 10, 12, 14 (no 8 × 16 = 128, overlap) (i₁) 7 bitsW2: all [note: maximum refinement gain for frequency selectiveprecoding] 2 W1: 0, 2, 4, 6, 8, 10, 12, 14 (no 8 × 2 = 16, overlap) (i₁)4 bits W2: for each W1, choose only (Y1, Y2) = (e1, e1) with all 2possible co-phasing [note: this resembles (N, Nb) = (8, 1) design] (i₂ =0-1) 3 W1: 0, 2 (no overlap) (i₁) 2 × 8 = 16, W2: for each W1, chooseonly 8 out of 4 bits 16 possible (Y1, Y2), e.g. the even indexed or thelast 8 (i₂ = 0, 2, . . . 14 or 8-15) 4 W1: 0, 2 (no overlap) (i₁) 2 × 8= 16, W2: all 4 bits 5 W1: 0 (fixed precoding) (i₁) 1, 0 bit 6 W1: 0(fixed precoding) (i₁) 1, 0 bit 7 W1: 0 (fixed precoding) (i₁) 1, 0 bit8 W1: 0 (i₁) 1, 0 bit

Table 19 shows a fourth example of sub-sampling of codebook C1+C2.

TABLE 19 No. W1 + W2 RI Chosen W1 + W2 index for sub-sampling hypotheses1 W1: all (i₁) 16 × 8 = 128, W2: for each W1, choose only Y = e1 and 7bits e2 with all 4 possible co-phasing [note: this resembles (N, Nb) =(32, 1) design] (i₂ = 0-7) 2 W1: 0, 2, 4, 6, 8, 10, 12, 14 (no 8 × 2 =18, overlap) (i₁) 4 bits W2: for each W1, choose only (Y1, Y2) = (e1,e1) with all 2 possible co-phasing [note: this resembles (N, Nb) =(8, 1) design] (i₂ = 0-1) 3 W1: 0, 2 (no overlap) (i₁) 2 × 8 = 16, W2:for each W1, choose only 8 out of 4 bits 16 possible (Y1, Y2), e.g. theeven indexed or the last 8 (i₂ = 0, 2, . . . 14 or 8-15) 4 W1: 0, 2 (nooverlap) (i₁) 2 × 8 = 16, W2: all 4 bits 5 W1: 0 (fixed precoding) (i₁)1, 0 bit 6 W1: 0 (fixed precoding) (i₁) 1, 0 bit 7 W1: 0 (fixedprecoding) (i₁) 1, 0 bit 8 W1: 0 (i₁) 1, 0 bit

For any of the above exemplary designs, it is possible to combine a partof one example with other part(s) from other examples. Furthermore, itis possible to use more than one (e.g. 2 or all 4) W1 matrices for ranks5, 6 and 7 for any of the above examples in Tables 16 to 19.

Feedback Payload Analysis

Based on the above codebook sub-sampling designs, the payload associatedwith each CSI mode can be compared below.

Table 20 shows a payload comparison for PUCCH mode 1-1 (bits).

TABLE 20 CSI mode 1 CSI mode 2 RI Report 1 Report 2 Report 1 Report 2 15(**) 8 3 10/11 2 5(**) 11 3 11 3 5(**) 11 3 11 4 5(**) 10 3 11 5 5 7 37 to 9 (*) 6 5 7 3 7 to 9 (*) 7 5 7 3 7 to 9 (*) 8 5 7 3  7 For entriesmarked with (*) the result depends on how many W1 precoding matrices areused for ranks 5, 6, and 7. Entries marked (**) may be reduced to 4 bitsif RI/W1 payload is to be variable and UE-specific depending on the UEcategory, for example the number of UE receive antennas or the maximumnumber of layers.Codebook Sub-Sampling for PUSCH

PUSCH feedback mode for 8 TX supports natural extension of Rel. 8 PUSCHreporting mode (1-2, 2-2, 3-1) under the double-codebook structure andconsiders Mode 3-2 with sub-band PMI+CQI for CQI accuracy enhancement inRel. 10. Considering the potentially larger payload and the use ofcarrier aggregation, the feedback overhead is reduced via codebooksub-sampling even further especially for the modes with sub-band PMIsuch as mode 1-2 and 3-2. Since W1 is wideband, there is no need toapply codebook sub-sampling in this case as the overhead is smallrelative to the rests. Codebook sub-sampling is applied only to W2 inthe context of PUSCH reporting modes 1-2 and 3-2.

Codebook sub-sampling may be more compelling for mode 3-2. This isbecause the sub-band W2 payload size is {4, 4, 4, 3} bits for rank {1,2, 3, 4}, which is also comparable to the payload in Rel. 8 mode 1-2. Onthe other hand, mode 3-2 consists of both sub-band CQI and sub-band PMI.

For the standard 8 TX codebook, W2 codebook sub-sampling can beperformed in different manners. The W1 codebook is not sub-sampled andall the possible W1 matrices are used. Some exemplary W2 codebooksub-sampling schemes for different sub-sampling size are given in Table21. While this is not exhaustive, the schemes given in Table 21 areexpected to perform well. Note the design in Table 21 satisfies a nestedproperty, so that the 1-bit W2 codebook is a subset of 2-bit W2codebook. Thus a 2-bit W2 codebook is a subset of the 3-bit W2 codebook.

Table 21 shows different W2 codebook sub-sampling schemes for PUSCH.

TABLE 21 W2 sub- sam- pling W2 sub-sampled codebook size Rank 1 Rank 2Rank 3 Rank 4 1-bit Y = e1 with (Y1, Y2) = [e1, e1] Choose only Y = [e1e5] only 2 out with all 2 2 out of 16 with all 2 of 4 co-phasingpossible co-phasing possible (Note this (Y1, Y2), (Note this co-phasingcorresponds to e.g. (e1, [e1 corresponds (e.g. BPSK i2 = 0, 1) e5])or([e1 to i2 = 0, 1) only +/−1) e5], e5) (Note this (Note thiscorresponds corresponds to i2 = 0, 2) to i2 = 0, 2) 2-bit Y = e1 with(Y1, Y2) = [e1, e1] Choose only Y = [e1 e5] or all 4 or [e3, e3] with 4out of 16 [e3 e7] co-phasing all 2 possible with all 2 (Note thisco-phasing (Y1, Y2), co-phasing corresponds (Note this e.g. (e1, [e1(Note this to i2 = 0, 1, corresponds to e5]), corresponds 2, 3) i2 = 0,1, 4, 5) (e3, [e3 to i2 = 0, 1, e7]), ([e1 4, 5) e5], e5), or ([e3 e7],e7) (Note this corresponds to i2 = 0, 2, 8, 10) 3-bit Y = e1 or e3 (Y1,Y2) = [e1, e1] Choose only No with all 4 or [e2, 8 out of 16sub-sampling co-phasing e2], [e3, e3], or possible (full set) (Note this[e4, e4] with (Y1, Y2), corresponds all 2 e.g. the to i2 = 0-3co-phasing even indexed and 8-11) (Note this or the last 8 correspondsto (Note this i2 = 0-7) corresponds to i2 = 0, 2, . . . 14, or i2 =8-15) 4-bit No No sub-sampling No n/a sub-sampling (full set)sub-sampling (full set) (full set)

For rank-2 with 3-bit sub-sampling, instead of choosing (Y1, Y2)=[e1,e1]or [e2,e2], [e3,e3], or [e4,e4], this invention chooses a N1 precodersfrom {[e1,e1], [e2, e2],[e3,e3], [e4,e4]} with 2-co-phasing and choosesa N2 precoders from {[e1 e2], [e2 e3], [e1 e4], [e2 e4]} with 2co-phasing, where N1+N2=8. Achieves a good performance tradeoff betweenULA and XPD antenna configurations. Example:

W2={[e1,e1], [e3, e3], [e1,e2], and [e1,e4]}, with 2-co-phasing;

W2={[e1,e1], [e3, e3], [e1,e2], and [e2,e4]}, with 2-co-phasing; and

W2={[e1,e1], [e3, e3], [e1,e4], and [e2,e4]}, with 2-co-phasing.

In these examples, it is possible to replace {[e1,e1], [e3,e3]} with{[e2,e2, [e4,e4]}. It is also possible to replace [e1,e2] with [e2,e3].Similarly, for rank-2 with 2-bit sub-sampling, it is possible to replace[e3,e3] with [e1,e2], or [e2,e3], or [e1,e4] or [e2,e4].

For rank-3, sub-sampling can be designed slightly differently. A fewexamples are listed in Table 22. For a 3-bit rank-3 codebook, thisinvention chooses 8 out of 16 possible codebook entries. The nestedproperty can be ensured where the 1-bit W2 is a subset of the 2-bit W2,while ½ bit W2 are subsets of 3-bits W2 codebook. This is satisfied inexamples 1, 2 and 3.

Table 22 shows different W2 codebook sub-sampling schemes for PUSCH forRank-3.

TABLE 22 W2 sub- sampling Example 1 Example 2 Example 3 Example 4 sizeRank 3 Rank 3 Rank 3 Rank 3 1-bit Choose only Choose only Choose onlyChoose only 2 out of 16 2 out of 16 2 out of 16 2 out of 16 possiblepossible possible possible (Y1, Y2), (Y1, Y2), (Y1, Y2), (Y1, Y2), e.g.(e1, [e1 e.g. (e1, [e1 e.g. (e1, [e1 e.g. (e1, [e1 e5]) or ([e1 e5]) or([e5 e5]) or ([e1 e5]) or ([e5 e5], e5) e1], e1) e5], e5) e1], e1) (Notethis (Note this (Note this (Note this corresponds correspondscorresponds corresponds to i2 = 0, 2) to i2 = 0, 3) to i2 = 0, 2) to i2= 0, 3) 2-bit Choose only Choose only Choose only Choose only 4 out of16 4 out of 16 4 out of 16 4 out of 16 possible possible possiblepossible (Y1, Y2), (Y1, Y2), (Y1, Y2), (Y1, Y2), e.g. (e1, [e1 e.g. (e1,[e1 e.g. (e1, [e1 e.g. (e1, [e1 e5]), e5]), e5]), e5]), (e3, [e3 (e3,[e3 (e3, [e3 (e3, [e3 e7]), ([e1 e7]), ([e5 e7]), ([e1 e7]), ([e5 e5],e5), or e1], e1), or e5], e5), or e1], e1), or ([e3 e7], e7) ([e7 e3],e3) ([e3 e7], e7) ([e7 e3], e3) (Note this (Note this (Note this (Notethis corresponds corresponds corresponds corresponds to i2 = 0, 2, to i2= 0, 3, to i2 = 0, 2, to i2 = 0, 3, 8, 10) 8, 11) 8, 10) 8, 11) 3-bitChoose 8 out Choose 8 out Choose only Choose only of 16 of 16 8 out of16 8 out of 16 possible possible possible possible (Y1, Y2), (Y1, Y2),(Y1, Y2), (Y1, Y2), e.g. even e.g. even e.g. the e.g. the indexedindexed even indexed even indexed entries from entries from (Note this(Note this the codebook the codebook corresponds corresponds (Note this(Note this to i2 = 0, to i2 = 0, corresponds corresponds 2, . . . 14 2,. . . 14 to i2 = 0, 1, to i2 = 0, 1, 2, 3, 8, 9, 2, 3, 8, 9, 10, 11) 10,11) 4-bit No No No No sub-sampling sub-sampling sub-samplingsub-sampling (full set) (full set) (full set) (full set)

We further note the following. For rank 1 it is possible to sub-samplethe W2 such that Y=[e1] with all 4 co-phasing are chosen. In this casethe effective rank-1 codebook becomes [N, Nb]=[16, 1] design with nosub-sampling for W1. The payload size for subband W2 is then reduced to2 bits. For rank3 it is also possible to sub-sample the W2 codebook suchthat every 4th of the 16 possible (Y1, Y2) are chosen. This results inthe following W2 codebook. The payload size of subband W2 is thenreduced to 2-bits.

${{W_{2} \in C_{2}} = \left\{ {\frac{1}{\sqrt{2}}\begin{bmatrix}Y_{1} & Y_{2} \\Y_{1} & {- Y_{2}}\end{bmatrix}} \right\}},{\left( {Y_{1},Y_{2}} \right) \in \begin{Bmatrix}\left( {e_{1},\left\lbrack {e_{1}\mspace{14mu} e_{5}} \right\rbrack} \right) \\\left( {e_{5},\left\lbrack {e_{1}\mspace{14mu} e_{5}} \right\rbrack} \right) \\\left( {\left\lbrack {e_{1}\mspace{14mu} e_{5}} \right\rbrack,e_{5}} \right) \\\left( {\left\lbrack {e_{5}\mspace{14mu} e_{1}} \right\rbrack,e_{1}} \right)\end{Bmatrix}}$For rank-4, it is possible to further sub-sample the W2 codebook suchthat only [e1 e5] and [e3 e7] are chosen for [Y1, Y2]. The payload sizeof subband W2 is then reduced to 2 bits.

${{W_{2} \in C_{2}} = \left\{ {{\frac{1}{\sqrt{2}}\begin{bmatrix}Y & Y \\Y & {- Y}\end{bmatrix}},{\frac{1}{\sqrt{2}}\begin{bmatrix}Y & Y \\{j\; Y} & {{- j}\; Y}\end{bmatrix}}} \right\}},{Y \in \left\{ {\left\lbrack {e_{1}\mspace{14mu} e_{5}} \right\rbrack,\left\lbrack {e_{3}\mspace{14mu} e_{7}} \right\rbrack} \right\}}$Thus one may generate any sub-sampling scheme with a combination of theschemes given in Table 22, where the sub-sampling size for rank-n (n=1,. . . 8) are different possibly. Some examples are given in Tables 23 to25.

Table 23 is an example of combination with different sizes acrossdifferent ranks

TABLE 23 No. W2 hypotheses RI Chosen W2 index for sub-sampling (bits) 1Y = e1 with all 4 possible W2 payload: co-phasing log2 (4) = 2 bits 2Choose only (Y1, Y2) = (e1, e1) with W2 payload: all 2 possibleco-phasing log2 (2) = 1 bit 3 Choose only 4 out of 16 possible W2payload: (Y1, Y2), e.g. every 4th entry log2 (4) = 2 bits 4 [Y1 Y2] =[e1, e5] and [e3 e7] W2 payload: log2 (4) = 2 bits 5 All 1, 0 bit 6 All1, 0 bit 7 All 1, 0 bit 8 All 1, 0 bit

Table 23 is an example of combination with different sizes acrossdifferent ranks.

TABLE 24 No. W2 hypotheses RI Chosen W2 index for sub-sampling (bits) 1Y = e1 and e3 with all 4 possible W2 payload: co-phasing log2 (8) = 3bits 2 Choose only (Y1, Y2) = (e1, e1) with W2 payload: all 2 possibleco-phasing log2 (2) = 1 bits 3 Choose only 8 out of 16 possible W2payload: (Y1, Y2), e.g. the even log2 (8) = 3 bits indexed or the last 84 All 1, 0 bit 5 All 1, 0 bit 6 All 1, 0 bit 7 All 1, 0 bit 8 All 1, 0bit

Table 25 is an example of this combination with different sizes acrossdifferent ranks.

TABLE 25 No. W2 Chosen W2 index for hypotheses RI sub-sampling (bits) 1Y = e1 and e3 with all 4 W2 payload: possible co-phasing log2 (8) = 3bits 2 Choose only (Y1, Y2) = (e1, e1) or W2 payload: (e3, e3) with all2 log2 (4) = 2 bits co-phasing 3 Choose only 4 out of 16 W2 payload:possible (Y1, Y2), e.g. log2 (4) = 2 bits every 4th entry 4 [Y1 Y2] =[e1, e5] and [e3 e7] W2 payload: log2 (4) = 2 bits 5 All 1, 0 bit 6 All1, 0 bit 7 All 1, 0 bit 8 All 1, 0 bit

The agreed standard 8 TX codebook can be written as shown below. Thecomposite precoder W is derived from W=W1*W2. The following notation isused:

{tilde over (e)}_(n) denotes a 4×1 selection vector with all zerosexcept for the n-th element with value 1; and

e_(n) denotes an 8×1 selection vector with all zeros except for the n-thelement with value 1.

Rank  1  and  2:${B = \left\lbrack {b_{0},{b_{1}\mspace{14mu}\ldots\mspace{14mu} b_{31}}} \right\rbrack},{\lbrack B\rbrack_{{1 + m},{1 + n}} = {\mathbb{e}}^{j\frac{2\pi\;{mn}}{32}}},{m = 0},1,2,3,{n = 0},1,\ldots\mspace{14mu},31$X^((k)) ∈ {[b_(2 k mod 32)b_((2k + 1) mod 32)b_((2k + 2)mod 32)b_((2k + 3)mod 32)]:  k = 0, 1, …  , 15}${W_{1}^{(k)} = \begin{bmatrix}X^{(k)} & 0 \\0 & X^{(k)}\end{bmatrix}},{C_{1} = \left\{ {W_{1}^{(0)},W_{1}^{(1)},W_{1}^{(2)},\ldots\mspace{14mu},W_{1}^{(15)}} \right\}}$Rank  1: ${{W_{2} \in C_{2}} = \left\{ {{\frac{1}{\sqrt{2}}\begin{bmatrix}Y \\Y\end{bmatrix}},{\frac{1}{\sqrt{2}}\begin{bmatrix}Y \\{j\; Y}\end{bmatrix}},{\frac{1}{\sqrt{2}}\begin{bmatrix}Y \\{- Y}\end{bmatrix}},{\frac{1}{\sqrt{2}}\begin{bmatrix}Y \\{{- j}\; Y}\end{bmatrix}}} \right\}},{Y \in \left\{ {{\overset{\sim}{e}}_{1},{\overset{\sim}{e}}_{2},{\overset{\sim}{e}}_{3},{\overset{\sim}{e}}_{4}} \right\}}$Rank  2: ${W_{2} \in C_{2}} = \left\{ {{\frac{1}{\sqrt{2}}\begin{bmatrix}Y \\Y\end{bmatrix}},{\frac{1}{\sqrt{2}}\begin{bmatrix}Y \\{j\; Y}\end{bmatrix}},{\frac{1}{\sqrt{2}}\begin{bmatrix}Y \\{- Y}\end{bmatrix}},{\frac{1}{\sqrt{2}}\begin{bmatrix}Y \\{{- j}\; Y}\end{bmatrix}}} \right\}$$\left( {Y_{1},Y_{1}} \right) \in \left\{ {\left( {{\overset{\sim}{e}}_{1},{\overset{\sim}{e}}_{1}} \right),\left( {{\overset{\sim}{e}}_{2},{\overset{\sim}{e}}_{2}} \right),\left( {{\overset{\sim}{e}}_{3},{\overset{\sim}{e}}_{3}} \right),\left( {{\overset{\sim}{e}}_{4},{\overset{\sim}{e}}_{4}} \right),\left( {{\overset{\sim}{e}}_{1},{\overset{\sim}{e}}_{2}} \right),\left( {{\overset{\sim}{e}}_{2},{\overset{\sim}{e}}_{3}} \right),\left( {{\overset{\sim}{e}}_{1},{\overset{\sim}{e}}_{4}} \right),\left( {{\overset{\sim}{e}}_{2},{\overset{\sim}{e}}_{4}} \right)} \right\}$Rank  3  and  4:${B = \left\lbrack {b_{0},{b_{1}\mspace{14mu}\ldots\mspace{14mu} b_{15}}} \right\rbrack},{\lbrack B\rbrack_{{1 + m},{1 + n}} = {\mathbb{e}}^{j\frac{2\pi\;{mn}}{16}}},{m = 0},1,2,3,{n = 0},1,\ldots\mspace{14mu},15$X^((k)) ∈ {[b_(4 k mod 16)b_((4k + 1) mod 16)  …  b_((4k + 7)mod 16)]:  k = 0, 1, 2, 3}${W_{1}^{(k)} = \begin{bmatrix}X^{(k)} & 0 \\0 & X^{(k)}\end{bmatrix}},{C_{1} = \left\{ {W_{1}^{(0)},W_{1}^{(1)},W_{1}^{(2)},\ldots\mspace{14mu},W_{1}^{(3)}} \right\}}$Rank  3:${{W_{2} \in C_{2}} = \left\{ {\frac{1}{\sqrt{2}}\begin{bmatrix}Y_{1} & Y_{2} \\Y_{1} & {- Y_{2}}\end{bmatrix}} \right\}},{\left( {Y_{1},Y_{2}} \right) \in \begin{Bmatrix}{\left( {e_{1},\left\lbrack {e_{1}\mspace{14mu} e_{5}} \right\rbrack} \right),\left( {e_{2},\left\lbrack {e_{2}\mspace{14mu} e_{6}} \right\rbrack} \right),\left( {e_{3},\left\lbrack {e_{3}\mspace{14mu} e_{7}} \right\rbrack} \right),\left( {e_{4},\left\lbrack {e_{4}\mspace{14mu} e_{8}} \right\rbrack} \right)} \\{\left( {e_{5},\left\lbrack {e_{1}\mspace{14mu} e_{5}} \right\rbrack} \right),\left( {e_{6},\left\lbrack {e_{2}\mspace{14mu} e_{6}} \right\rbrack} \right),\left( {e_{7},\left\lbrack {e_{3}\mspace{14mu} e_{7}} \right\rbrack} \right),\left( {e_{8},\left\lbrack {e_{4}\mspace{14mu} e_{8}} \right\rbrack} \right)} \\{\left( {\left\lbrack {e_{1}\mspace{14mu} e_{5}} \right\rbrack,e_{5}} \right),\left( {\left\lbrack {e_{2}\mspace{14mu} e_{6}} \right\rbrack,e_{6}} \right),\left( {\left\lbrack {e_{3}\mspace{14mu} e_{7}} \right\rbrack,e_{7}} \right),\left( {\left\lbrack {e_{4}\mspace{14mu} e_{8}} \right\rbrack,e_{8}} \right)} \\{\left( {\left\lbrack {e_{5}\mspace{14mu} e_{1}} \right\rbrack,e_{1}} \right),\left( {\left\lbrack {e_{6}\mspace{14mu} e_{2}} \right\rbrack,e_{2}} \right),\left( {\left\lbrack {e_{7}\mspace{14mu} e_{3}} \right\rbrack,e_{3}} \right),\left( {\left\lbrack {e_{8}\mspace{14mu} e_{4}} \right\rbrack,e_{4}} \right)}\end{Bmatrix}}$ Rank  4:${{W_{2} \in C_{2}} = \left\{ {{\frac{1}{\sqrt{2}}\begin{bmatrix}Y & Y \\Y & {- Y}\end{bmatrix}},{\frac{1}{\sqrt{2}}\begin{bmatrix}Y & Y \\{j\; Y} & {{- j}\; Y}\end{bmatrix}}} \right\}},{Y \in \left\{ {\left\lbrack {e_{1}\mspace{14mu} e_{5}} \right\rbrack,\left\lbrack {e_{2}\mspace{14mu} e_{6}} \right\rbrack,\left\lbrack {e_{3}\mspace{14mu} e_{7}} \right\rbrack,\left\lbrack {e_{4}\mspace{14mu} e_{8}} \right\rbrack} \right\}}$Rank  5  to  7:$X^{(k)} = {{diag}\left\{ {1,{\mathbb{e}}^{j\frac{\pi}{8}k},{\mathbb{e}}^{j\frac{\pi}{4}k},{\mathbb{e}}^{j\frac{3\pi}{8}k}} \right\} \times \begin{bmatrix}1 & 1 & 1 & 1 \\1 & j & {- 1} & {- j} \\1 & {- 1} & 1 & {- 1} \\1 & {- j} & {- 1} & j\end{bmatrix}}$ ${W_{1} \in C_{1}} = \left\{ {\begin{bmatrix}X^{(0)} & 0 \\0 & X^{(0)}\end{bmatrix},\begin{bmatrix}X^{(1)} & 0 \\0 & X^{(1)}\end{bmatrix},\begin{bmatrix}X^{(2)} & 0 \\0 & X^{(2)}\end{bmatrix},\begin{bmatrix}X^{(3)} & 0 \\0 & X^{(3)}\end{bmatrix}} \right\}$ Rank  5:$W_{2} = {\frac{1}{\sqrt{2}}\begin{bmatrix}{\overset{\sim}{e}}_{1} & {\overset{\sim}{e}}_{1} & {\overset{\sim}{e}}_{2} & {\overset{\sim}{e}}_{2} & {\overset{\sim}{e}}_{3} \\{\overset{\sim}{e}}_{1} & {- {\overset{\sim}{e}}_{1}} & {\overset{\sim}{e}}_{2} & {- {\overset{\sim}{e}}_{2}} & {\overset{\sim}{e}}_{3}\end{bmatrix}}$ Rank  6: $W_{2} = {\frac{1}{\sqrt{2}}\begin{bmatrix}{\overset{\sim}{e}}_{1} & {\overset{\sim}{e}}_{1} & {\overset{\sim}{e}}_{2} & {\overset{\sim}{e}}_{2} & {\overset{\sim}{e}}_{3} & {\overset{\sim}{e}}_{3} \\{\overset{\sim}{e}}_{1} & {- {\overset{\sim}{e}}_{1}} & {\overset{\sim}{e}}_{2} & {- {\overset{\sim}{e}}_{2}} & {\overset{\sim}{e}}_{3} & {- {\overset{\sim}{e}}_{3}}\end{bmatrix}}$ Rank  7: $W_{2} = {\frac{1}{\sqrt{2}}\begin{bmatrix}{\overset{\sim}{e}}_{1} & {\overset{\sim}{e}}_{1} & {\overset{\sim}{e}}_{2} & {\overset{\sim}{e}}_{2} & {\overset{\sim}{e}}_{3} & {\overset{\sim}{e}}_{3} & {\overset{\sim}{e}}_{4} \\{\overset{\sim}{e}}_{1} & {- {\overset{\sim}{e}}_{1}} & {\overset{\sim}{e}}_{2} & {- {\overset{\sim}{e}}_{2}} & {\overset{\sim}{e}}_{3} & {- {\overset{\sim}{e}}_{3}} & {\overset{\sim}{e}}_{4}\end{bmatrix}}$ Rank  8: ${X^{(0)} = \begin{bmatrix}1 & 1 & 1 & 1 \\1 & j & {- 1} & {- j} \\1 & {- 1} & 1 & {- 1} \\1 & {- j} & {- 1} & j\end{bmatrix}},{W_{1} = \begin{bmatrix}X^{(0)} & 0 \\0 & X^{(0)}\end{bmatrix}}$ Rank  8: $W_{2} = {\frac{1}{\sqrt{2}}\begin{bmatrix}{\overset{\sim}{e}}_{1} & {\overset{\sim}{e}}_{1} & {\overset{\sim}{e}}_{2} & {\overset{\sim}{e}}_{2} & {\overset{\sim}{e}}_{3} & {\overset{\sim}{e}}_{3} & {\overset{\sim}{e}}_{4} & {\overset{\sim}{e}}_{4} \\{\overset{\sim}{e}}_{1} & {- {\overset{\sim}{e}}_{1}} & {\overset{\sim}{e}}_{2} & {- {\overset{\sim}{e}}_{2}} & {\overset{\sim}{e}}_{3} & {- {\overset{\sim}{e}}_{3}} & {\overset{\sim}{e}}_{4} & {- {\overset{\sim}{e}}_{4}}\end{bmatrix}}$

FIG. 4 is a block diagram illustrating internal details of an eNB 1002and a mobile UE 1001 in the network system of FIG. 1. Mobile UE 1001 mayrepresent any of a variety of devices such as a server, a desktopcomputer, a laptop computer, a cellular phone, a Personal DigitalAssistant (PDA), a smart phone or other electronic devices. In someembodiments, the electronic mobile UE 1001 communicates with eNB 1002based on a LTE or Evolved Universal Terrestrial Radio Access Network(E-UTRAN) protocol. Alternatively, another communication protocol nowknown or later developed can be used.

Mobile UE 1001 comprises a processor 1010 coupled to a memory 1012 and atransceiver 1020. The memory 1012 stores (software) applications 1014for execution by the processor 1010. The applications could comprise anyknown or future application useful for individuals or organizations.These applications could be categorized as operating systems (OS),device drivers, databases, multimedia tools, presentation tools,Internet browsers, emailers, Voice-Over-Internet Protocol (VOIP) tools,file browsers, firewalls, instant messaging, finance tools, games, wordprocessors or other categories. Regardless of the exact nature of theapplications, at least some of the applications may direct the mobile UE1001 to transmit UL signals to eNB (base-station) 1002 periodically orcontinuously via the transceiver 1020. In at least some embodiments, themobile UE 1001 identifies a Quality of Service (QoS) requirement whenrequesting an uplink resource from eNB 1002. In some cases, the QoSrequirement may be implicitly derived by eNB 1002 from the type oftraffic supported by the mobile UE 1001. As an example, VOIP and gamingapplications often involve low-latency uplink (UL) transmissions whileHigh Throughput (HTP)/Hypertext Transmission Protocol (HTTP) traffic caninvolve high-latency uplink transmissions.

Transceiver 1020 includes uplink logic which may be implemented byexecution of instructions that control the operation of the transceiver.Some of these instructions may be stored in memory 1012 and executedwhen needed by processor 1010. As would be understood by one of skill inthe art, the components of the uplink logic may involve the physical(PHY) layer and/or the Media Access Control (MAC) layer of thetransceiver 1020. Transceiver 1020 includes one or more receivers 1022and one or more transmitters 1024.

Processor 1010 may send or receive data to various input/output devices1026. A subscriber identity module (SIM) card stores and retrievesinformation used for making calls via the cellular system. A Bluetoothbaseband unit may be provided for wireless connection to a microphoneand headset for sending and receiving voice data. Processor 1010 maysend information to a display unit for interaction with a user of mobileUE 1001 during a call process. The display may also display picturesreceived from the network, from a local camera, or from other sourcessuch as a Universal Serial Bus (USB) connector. Processor 1010 may alsosend a video stream to the display that is received from various sourcessuch as the cellular network via RF transceiver 1020 or the camera.

During transmission and reception of voice data or other applicationdata, transmitter 1024 may be or become non-synchronized with itsserving eNB. In this case, it sends a random access signal. As part ofthis procedure, it determines a preferred size for the next datatransmission, referred to as a message, by using a power threshold valueprovided by the serving eNB, as described in more detail above. In thisembodiment, the message preferred size determination is embodied byexecuting instructions stored in memory 1012 by processor 1010. In otherembodiments, the message size determination may be embodied by aseparate processor/memory unit, by a hardwired state machine, or byother types of control logic, for example.

eNB 1002 comprises a Processor 1030 coupled to a memory 1032, symbolprocessing circuitry 1038, and a transceiver 1040 via backplane bus1036. The memory stores applications 1034 for execution by processor1030. The applications could comprise any known or future applicationuseful for managing wireless communications. At least some of theapplications 1034 may direct eNB 1002 to manage transmissions to or frommobile UE 1001.

Transceiver 1040 comprises an uplink Resource Manager, which enables eNB1002 to selectively allocate uplink Physical Uplink Shared CHannel(PUSCH) resources to mobile UE 1001. As would be understood by one ofskill in the art, the components of the uplink resource manager mayinvolve the physical (PHY) layer and/or the Media Access Control (MAC)layer of the transceiver 1040. Transceiver 1040 includes at least onereceiver 1042 for receiving transmissions from various UEs within rangeof eNB 1002 and at least one transmitter 1044 for transmitting data andcontrol information to the various UEs within range of eNB 1002.

The uplink resource manager executes instructions that control theoperation of transceiver 1040. Some of these instructions may be locatedin memory 1032 and executed when needed on processor 1030. The resourcemanager controls the transmission resources allocated to each UE 1001served by eNB 1002 and broadcasts control information via the PDCCH.

Symbol processing circuitry 1038 performs demodulation using knowntechniques. Random access signals are demodulated in symbol processingcircuitry 1038.

During transmission and reception of voice data or other applicationdata, receiver 1042 may receive a random access signal from a UE 1001.The random access signal is encoded to request a message size that ispreferred by UE 1001. UE 1001 determines the preferred message size byusing a message threshold provided by eNB 1002. In this embodiment, themessage threshold calculation is embodied by executing instructionsstored in memory 1032 by processor 1030. In other embodiments, thethreshold calculation may be embodied by a separate processor/memoryunit, by a hardwired state machine, or by other types of control logic,for example. Alternatively, in some networks the message threshold is afixed value that may be stored in memory 1032, for example. In responseto receiving the message size request, eNB 1002 schedules an appropriateset of resources and notifies UE 1001 with a resource grant.

What is claimed is:
 1. A method of channel state information (CSI)feedback for communication between a base station (eNB) and a pluralityof user equipment (UE), comprising the steps of: each user equipmenttransmitting via Physical Uplink Control CHannel (PUCCH) a CSI feedbacksignal having: a first mode with a first report jointly coding RankIndicator (RI) and a first precoding matrix (W1), and with a secondreport coding Channel Quality Indicator (CQI) and a second precodingmatrix (W2), and a second mode with a first report coding Rank Indicator(RI), and with a second report coding Channel Quality Indicator (CQI)and jointly coding the first precoding matrix (W1) and the secondprecoding matrix (W2); wherein said step of jointly coding RankIndicator (RI) and the first precoding matrix (W1) employs codebooksub-sampling; wherein said step of jointly coding the first precodingmatrix (W1) and the second precoding matrix (W2) employs codebooksub-sampling; and wherein said step of jointly coding Rank Indicator(RI) and the first precoding matrix (W1) employs codebook sub-samplinginto a maximum of 5 bits as follows: RI Chosen W1 index for sub-sampling(i₁) 1 0, 2, 4, 6, 8, 10, 12, 14 (no overlap) 2 0, 2, 4, 6, 8, 10, 12,14 (no overlap) 3 0, 2 (no overlap) 4 0, 2 (no overlap).


2. The method of claim 1, wherein: sub-sampling of the first precodingmatrix (W1) skips W1 matrices with overlapping beams.
 3. A method ofchannel state information (CSI) feedback for communication between abase station (eNB) and a plurality of user equipment (UE), comprisingthe steps of: each user equipment transmitting via Physical UplinkControl CHannel (PUCCH) a CSI feedback signal having: a first mode witha first report jointly coding Rank Indicator (RI) and a first precodingmatrix (W1), and with a second report coding Channel Quality Indicator(CQI) and a second precoding matrix (W2), and a second mode with a firstreport coding Rank Indicator (RI), and with a second report codingChannel Quality Indicator (CQI) and jointly coding the first precodingmatrix (W1) and the second precoding matrix (W2); wherein said step ofjointly coding Rank Indicator (RI) and the first precoding matrix (W1)employs codebook sub-sampling; wherein said step of jointly coding thefirst precoding, matrix (W1) and the second precoding matrix (W2)employs codebook sub-sampling; and wherein said step of jointly codingRank Indicator (RI) and the first precoding matrix (W1) employs codebooksub-sampling into a maximum of 5 bits as follows: RI Chosen W1 index forsub-sampling (i₁) 1 0, 2, 4, 6, 8, 10, 12, 14 (no overlap) 2 0, 2, 4, 6,8, 10, 12, 14 (no overlap) 3 0, 1, 2, 3 (all) 4 0, 1, 2, 3 (all).


4. A method of channel state information (CSI) feedback forcommunication between a base station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipmenttransmitting via Physical Uplink Control CHannel (PUCCH) a CSI feedbacksignal having: a first mode with a first report jointly coding RankIndicator (RI) and a first precoding matrix (W1), and with a secondreport coding Channel Quality Indicator (CQI) and a second precodingmatrix (W2), and a second mode with a first report coding Rank Indicator(RI), and with a second report coding Channel Quality Indicator (CQI)and jointly coding the first precoding matrix (W1) and the secondprecoding matrix (W2); wherein said step of jointly coding RankIndicator (RI) and the first precoding matrix (W1) employs codebooksub-sampling; wherein said step of jointly coding the first precodingmatrix (W1) and the second precoding matrix (W2) employs codebooksub-sampling; and wherein said step of jointly coding Rank Indicator(RI) and the first precoding matrix (W1) employs codebook sub-samplinginto a maximum of 5 bits as follows: RI Chosen W1 index for sub-sampling(i₁) 1 0, 2, 4, 6, 8, 10, 12, 14 (no overlap) 2 0, 2, 4, 6, 8, 10, 12,14 (no overlap) 3 0, 1, 2, 3 (all) 4 0, 1, 2, 3 (all) 5 0, 1 (use 2 outof 4) 6 0, 1 (use 2 out of 4) 7 0, 1 (use 2 out of 4) 8
 0.


5. A method of channel state information (CSI) feedback forcommunication between a base station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipmenttransmitting via Physical Uplink Control CHannel (PUCCH) a CSI feedbacksignal having: a first mode with a first report jointly coding RankIndicator (RI) and a first precoding matrix (W1), and with a secondreport coding Channel Quality Indicator (CQI) and a second precodingmatrix (W2), and a second mode with a first report coding Rank Indicator(RI), and with a second report coding Channel Quality Indicator (CQI)and jointly coding the first precoding matrix (W1) and the secondprecoding matrix (W2); wherein said step of jointly coding RankIndicator (RI) and the first precoding matrix (W1) employs codebooksub-sampling; wherein said step of jointly coding the first precodingmatrix (W1) and the second precoding matrix (W2) employs codebooksub-sampling; and wherein said step of jointly coding Rank Indicator(RI) and the first precoding matrix (W1) employs codebook sub-samplinginto a maximum of 5 bits as follows: RI Chosen W1 index for sub-sampling(i₁) 1 0, 2, 4, 6, 8, 10, 12, 14 (no overlap) 2 0-15 3 0, 2 (no overlap)4 0, 2 (no overlap).


6. A method of channel state information (CSI) feedback forcommunication between a base station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipmenttransmitting via Physical Uplink Control CHannel (PUCCH) a CSI feedbacksignal having: a first mode with a first report jointly coding RankIndicator (RI) and a first precoding matrix (W1), and with a secondreport coding Channel Quality Indicator (CQI) and a second precodingmatrix (W2), and a second mode with a first report coding Rank Indicator(RI), and with a second report coding Channel Quality Indicator (CQI)and jointly coding the first precoding matrix (W1) and the secondprecoding matrix (W2); wherein said step of jointly coding RankIndicator (RI) and the first precoding matrix (W1) employs codebooksub-sampling; wherein said step of jointly coding the first precodingmatrix (W1) and the second precoding matrix (W2) employs codebooksub-sampling; and wherein said step of jointly coding Rank Indicator(RI) and the first precoding matrix (W1) employs codebook sub-samplinginto a maximum of 5 bits as follows: RI Chosen W1 index for sub-sampling(i₁) 1 0-15 2 0, 2, 4, 6, 8, 10, 12, 14 (no overlap) 3 0, 2 (no overlap)4 0, 2 (no overlap).


7. A method of channel state information (CSI) feedback forcommunication between a base station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipmenttransmitting via Physical Uplink Control CHannel (PUCCH) a CSI feedbacksignal having: a first mode with a first report jointly coding RankIndicator (RI) and a first precoding matrix (W1), and with a secondreport coding Channel Quality Indicator (CQI) and a second precodingmatrix (W2), and a second mode with a first report coding Rank Indicator(RI), and with a second report coding Channel Quality indicator (CQI)and jointly coding the first precoding matrix (W1) and the secondprecoding matrix (W2); wherein said step of jointly coding RankIndicator (RI) and the first precoding matrix (W1) employs codebooksub-sampling; wherein said step of jointly coding the first precodingmatrix (W1) and the second precoding matrix (W2) employs codebooksub-sampling; and wherein for a 2-layer capable UE said step of jointlycoding Rank Indicator (RI) and the first precoding matrix (W1) employscodebook sub-sampling into 4 bits as follows: RI Chosen W1 index forsub-sampling (i₁) 1 0, 2, 4, 6, 8, 10, 12, 14 (no overlap) 2 0, 2, 4, 6,8, 10, 12, 14 (no overlap).


8. A method of channel state information (CSI) feedback forcommunication between a base station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipmenttransmitting via Physical Uplink Control CHannel (PUCCH) a CSI feedbacksignal having: a first mode with a first report jointly coding RankIndicator (RI) and a first precoding matrix (W1), and with a secondreport coding Channel Quality Indicator (CQI) and a second precodingmatrix (W2), and a second mode with a first report coding Rank Indicator(RI), and with a second report coding Channel Quality Indicator (CQI)and jointly coding the first precoding matrix (W1) and the secondprecoding matrix (W2); wherein said step of jointly coding RankIndicator (RI) and the first precoding matrix (W1) employs codebooksub-sampling; wherein said step of jointly coding the first precodingmatrix (W1) and the second precoding matrix (W2) employs codebooksub-sampling; and wherein for a 2-layer capable UE said step of jointlycoding Rank Indicator (RI) and the first precoding matrix (W1) employscodebook sub-sampling into 5 bits as follows: RI Chosen W1 index forsub-sampling (i₁) 1 0, 2, 4, 6, 8, 10, 12, 14 (no overlap) 2 0-15.


9. A method of channel state information (CSI) feedback forcommunication between a base station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipmenttransmitting via Physical Uplink Control CHannel (PUCCH) a CSI feedbacksignal having: a first mode with a first report jointly coding RankIndicator (RI) and a first precoding matrix (W1), and with a secondreport coding Channel Quality Indicator (CQI) and a second precodingmatrix (W2), and a second mode with a first report coding Rank Indicator(RI), and with a second report coding Channel Quality Indicator (CQI)and jointly coding the first precoding matrix (W1) and the secondprecoding matrix (W2), wherein said step of jointly coding RankIndicator (RI) and the first precoding matrix (W1) employs codebooksub-sampling; wherein said step of jointly coding the first precodingmatrix (W1) and the second precoding matrix (W2) employs codebooksub-sampling; and wherein for a 2-layer capable UE said step of jointlycoding Rank Indicator (RI) and the first precoding matrix (W1) employscodebook sub-sampling into 5 bits as follows: RI Chosen W1 index forsub-sampling (i₁) 1 0-15 2 0, 2, 4, 6, 8, 10, 12, 14 (no overlap).


10. A method of channel state information (CSI) feedback forcommunication between a base station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipmenttransmitting via Physical Uplink Control CHannel (PUCCH) a CSI feedbacksignal having: a first mode with a first report jointly coding RankIndicator (RI) and a first precoding matrix (W1), and with a secondreport coding Channel Quality Indicator (CQI) and a second precodingmatrix (W2), and a second mode with a first report coding Rank Indicator(RI), and with a second report coding Channel Quality indicator (CQI)and jointly coding the first precoding matrix (W1) and the secondprecoding matrix (W2); wherein said step of jointly coding RankIndicator (RI) and the first precoding matrix (W1) employs codebooksub-sampling; wherein said step of jointly coding the first precodingmatrix (W1) and the second precoding matrix (W2) employs codebooksub-sampling; and wherein for a 4-layer capable UE said step of jointlycoding Rank Indicator (RI) and the first precoding matrix (W1) employscodebook sub-sampling into 5 bits as follows: RI Chosen W1 index forsub-sampling (i₁) 1 0, 2, 4, 6, 8, 10, 12, 14 (no overlap) 2 0-15 3 0-34 0-3.


11. A method of channel state information (CSI) feedback forcommunication between a base station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipmenttransmitting via Physical Uplink Control CHannel (PUCCH) a CSI feedbacksignal having: a first mode with a first report jointly coding RankIndicator (RI) and a first precoding matrix (W1), and with a secondreport coding Channel Quality Indicator (CQI) and a second precodingmatrix (W2), and a second mode with a first report coding Rank Indicator(RI), and with a second report coding Channel Quality Indicator (CQI)and jointly coding the first precoding matrix (W1) and the secondprecoding matrix (W2); wherein said step of jointly coding RankIndicator (RI) and the first precoding matrix (W1) employs codebooksub-sampling; wherein said step of jointly coding the first precodingmatrix (W1) and the second precoding matrix (W2) employs codebooksub-sampling; and wherein for a 2-layer capable UE said step of jointlycoding Rank Indicator (RI) and the first precoding matrix (W1) employscodebook sub-sampling into 5 bits as follows: RI Chosen W1 index forsub-sampling (i₁) 1 0-15 2 0, 2, 4, 6, 8, 10, 12, 14 (no overlap) 3 0-34 0-3.


12. A method of channel state information (CSI) feedback forcommunication between a base station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipmenttransmitting via Physical Uplink Control CHannel (PUCCH) a CSI feedbacksignal having: a first mode with a first report jointly coding RankIndicator (RI) and a first precoding matrix (W1), and with a secondreport coding Channel Quality Indicator (CQI) and a second precodingmatrix (W2), and a second mode with a first report coding Rank Indicator(RI), and with a second report coding Channel Quality Indicator (CQI)and jointly coding the first precoding matrix (W1) and the secondprecoding matrix (W2); wherein said step of jointly coding RankIndicator (RI) and the first precoding matrix (W1) employs codebooksub-sampling; wherein said step of jointly coding the first precodingmatrix (W1) and the second precoding matrix (W2) employs codebooksub-sampling; and wherein for a 4-layer capable UE said step of jointlycoding Rank indicator (RI) and the first precoding matrix (W1) employscodebook sub-sampling into 5 bits as follows: RI Chosen W1 index forsub-sampling (i₁) 1 0, 2, 4, 6, 8, 10, 12, 14 (no overlap) 2 0, 2, 4, 6,8, 10, 12, 14 (no overlap) 3 0-3 4 0-3.


13. A method of channel state information (CSI) feedback forcommunication between a base station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipmenttransmitting via Physical Uplink Control CHannel (PUCCH) a CSI feedbacksignal having: a first mode with a first report jointly coding RankIndicator (RI) and a first precoding matrix (W1), and with a secondreport coding Channel Quality Indicator (CQI) and a second precodingmatrix (W2), and a second mode with a first report coding Rank Indicator(RI), and with a second report coding Channel Quality Indicator (CQI)and jointly coding the first precoding matrix (W1) and the secondprecoding matrix (W2); wherein said step of jointly coding RankIndicator (RI) and the first precoding matrix (W1) employs codebooksub-sampling; wherein said step of jointly coding the first precodingmatrix (W1) and the second precoding matrix (W2) employs codebooksub-sampling; and wherein said step of jointly coding Rank Indicator(RI) and the first precoding matrix (W1) employs codebook sub-samplingselecting indices for the first precoding matrix (W1) as follows: R1Chosen W1 index for sub-sampling 1 0, 2, 4, 6, 8, 10, 12, 14 (nooverlapping beams) 2 0, 2, 4, 6, 8, 10, 12, 14 (no overlapping beams) 30, 2 (no overlapping beams) 4 0, 2 (no overlapping beams) 5 0, 1 (use 2out of 4) 6 0, 1 (use 2 out of 4) 7 0, 1 (use 2 out of 4) 8
 0.


14. A method of channel state information (CSI) feedback forcommunication between a base station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipmenttransmitting via Physical Uplink Control CHannel (PUCCH) a CSI feedbacksignal having: a first mode with a first report jointly coding RankIndicator (RI) and a first precoding matrix (W1), and with a secondreport coding Channel Quality Indicator (CQI) and a second precodingmatrix (W2), and a second mode with a first report coding Rank Indicator(RI), and with a second report coding Channel Quality Indicator (CQI)and jointly coding the first precoding matrix (W1) and the secondprecoding matrix (W2); wherein said step of jointly coding RankIndicator (RI) and the first precoding matrix (W1) employs codebooksub-sampling; wherein said step of jointly coding the first precodingmatrix (W1) and the second precoding matrix (W2) employs codebooksub-sampling; and wherein said step of jointly coding the firstprecoding matrix (W1) and the second precoding matrix (W2) employscodebook sub-sampling: for rank equal one joint coding the firstprecoding matrix (W1) and the second precoding matrix (W2) employs 7bits or less, and for rank greater than one joint coding the firstprecoding matrix (W1) and the second precoding matrix (W2) employs 4bits or less.
 15. A method of channel state information (CSI) feedbackfor communication between a base station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipmenttransmitting via Physical Uplink Control Channel (PUCCH) a CSI feedbacksignal having: a first mode with a first report jointly coding RankIndicator (RI) and a first precoding matrix (W1), and with a secondreport coding Channel Quality Indicator (CQI) and a second precodingmatrix (W2), and a second mode with a first report coding Rank Indicator(RI), and with a second report coding Channel Quality Indicator (CQI)and jointly coding the first precoding matrix (W1) and the secondprecoding matrix (W2); wherein said step of jointly coding RankIndicator (RI) and the first precoding matrix (W1) employs codebooksub-sampling; wherein said step of jointly coding the first precodingmatrix (W1) and the second precoding matrix (W2) employs codebooksub-sampling; and wherein said step of jointly coding the firstprecoding matrix (W1) and the second precoding matrix (W2) employscodebook sub-sampling as follows: RI Chosen W1 + W2 index forsub-sampling 1 W1: 0, 2, 4, 6, 8, 10, 12, 14 (no overlap) (i₁) W2: foreach W1, choose only Y = e1 and e3 with all 4 possible co-phasing [note:this resembles (N, Nb) = (16, 1) design] (i₂ = 0-3, 8-11) 2 W1: 0, 2, 4,6, 8, 10, 12, 14 (no overlap) (i₁) W2: for each W1, choose only (Y1, Y2)= (e1, e1) with all 2 possible co-phasing [note: this resembles (N, Nb)= (8, 1) design] (i₂ = 0-1) 3 W1: 0, 2 (no overlap) (i₁) W2: for eachW1, choose only 8 out of 16 possible (Y1, Y2), e.g. the even indexed orthe last 8 (i₂ = 0, 2, . . . 14 or 8-15) 4 W1: 0, 2 (no overlap) (i₁)W2: all.


16. A method of channel state information (CSI) feedback forcommunication between a base station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipmenttransmitting via Physical Uplink Control Channel (PUCCH) a CSI feedbacksignal having: a first mode with a first report jointly coding RankIndicator (RI) and a first precoding matrix (WI), and with a secondreport coding Channel Quality Indicator (CQI) and a second precodingmatrix (W2); and a second mode with a first report coding Rank Indicator(RI), and with a second report coding Channel Quality Indicator (CQI)and jointly coding the first precoding matrix (W1) and the secondprecoding matrix (W2); wherein said step of jointly coding RankIndicator (RI) and the first precoding matrix (W1) employs codebooksub-sampling; wherein said step of jointly coding the first precodingmatrix (W1) and the second precoding matrix (W2) employs codebooksub-sampling; and wherein said step of jointly coding the firstprecoding matrix (W1) and the second precoding matrix (W2) employscodebook sub-sampling as follows: RI Chosen W1 + W2 index forsub-sampling 1 W1: all (i₁) W2: for each W1, choose only Y = el with all4 possible co-phasing [note: this resembles (N, Nb) = (16, I) design](i₂ = 0-3) 2 W1: 0, 2, 4, 6, 8, 10, 12, 14 (no overlap) (i₁) W2: foreach W1, choose only (Y1, Y2) = (el, el) with all 2 possible co-phasing[note: this resembles (N, Nb) = (8, 1) design] (i₂ = 0-1) 3 W1: 0, 2 (nooverlap) (i₁) W2: for each W1, choose only 8 out of 16 possible (Y1,Y2), e.g. the even indexed or the last 8 (i₂ = 0, 2 . . . 14 or 8-15) 4W1: 0, 2 (no overlap) (i₁) W2: all 5 W1: 0 (fixed precoding) (i₁) 6 W1:0 (fixed precoding) (i₁) 7 W1: 0 (fixed precoding) (i₁) 8 W1: 0 (i₁).


17. A method of channel state information (CSI) feedback forcommunication between a base station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipmenttransmitting via Physical Uplink Control CHannel (PUCCH) a CSI feedbacksignal having: a first mode with a first report jointly coding RankIndicator (RI) and a first precoding matrix (W1), and with a secondreport coding Channel Quality Indicator (CQI) and a second precodingmatrix (W2), and a second mode with a first report coding Rank Indicator(RI), and with a second report coding Channel Quality Indicator (CQI)and jointly coding the first precoding matrix (W1) and the secondprecoding matrix (W2); wherein said step of jointly coding RankIndicator (RI) and the first precoding matrix (W1) employs codebooksub-sampling; wherein said step of jointly coding the first precodingmatrix (W1) and the second precoding matrix (W2) employs codebooksub-sampling; and wherein said step of jointly coding the firstprecoding matrix (W1) and the second precoding matrix (W2) employscodebook sub-sampling as follows: RI Chosen W1 + W2 index forsub-sampling 1 W1: 0, 2, 4, 6, 8, 10, 12, 14 (no overlap) (i₁) W2: all[note: maximum refinement gain for frequency selective precoding] 2 W1:0, 2, 4, 6, 8, 10, 12, 14 (no overlap) (i₁) W2: for each W1, choose only(Y1, Y2) = (e1, e1) with all 2 possible co-phasing [note: this resembles(N, Nb) = (8, 1) design] (i₂ = 0-1) 3 W1: 0, 2 (no overlap) (i₁) W2: foreach W1, choose only 8 out of 16 possible (Y1, Y2), e.g. the evenindexed or the last 8 (i₂ = 0, 2, . . . 14 or 8-15) 4 W1: 0, 2 (nooverlap) (i₁) W2: all.


18. A method of channel state information (CSI) feedback forcommunication between a base station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipmenttransmitting via Physical Uplink Control CHannel (PUCCH) a CSI feedbacksignal having: a first mode with a first report jointly coding RankIndicator (RI) and a first precoding matrix (W1), and with a secondreport coding Channel Quality Indicator (CQI) and a second precodingmatrix (W2), and a second mode with a first report coding Rank Indicator(RI), and with a second report coding Channel Quality Indicator (CQI)and jointly coding the first precoding matrix (W1) and the secondprecoding matrix (W2); wherein said step of jointly coding RankIndicator (RI) and the first precoding matrix (W1) employs codebooksub-sampling; wherein said step of jointly coding the first precodingmatrix (W1) and the second precoding matrix (W2) employs codebooksub-sampling; and wherein said step of jointly coding the firstprecoding matrix (W1) and the second precoding matrix (W2) employscodebook sub-sampling as follows: RI Chosen W1 + W2 index forsub-sampling 1 W1: all (i₁) W2: for each W1, choose only Y = e1 and e2with all 4 possible co-phasing [note: this resembles (N, Nb) = (32, 1)design] (i₂ = 0-7) 2 W1: 0, 2, 4, 6, 8, 10, 12, 14 (no overlap) (i₁) W2:for each W1, choose only (Y1, Y2) = (e1, e1) with all 2 possibleco-phasing [note: this resembles (N, Nb) = (8, 1) design] (i₂ = 0-1) 3W1: 0, 2 (no overlap) (i₁) W2: for each W1, choose only 8 out of 16possible (Y1, Y2), e.g. the even indexed or the last 8 (i₂ = 0, 2, . . .14 or 8-15) 4 W1: 0, 2 (no overlap) (i₁) W2: all 5 W1: 0 (fixedprecoding) (i₁) 6 W1: 0 (fixed precoding) (i₁) 7 W1: 0 (fixed precoding)(i₁) 8 W1: 0 (i₁).


19. A method of channel state information (CSI) feedback forcommunication between a base station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipment reportingvia a Physical Uplink Shared Channel (PUSCH) a CSI feedback signalincluding a rank indicator (RI) and at least one of the set including achannel quality indicator (CQI), a first precoding matrix (W1) and asecond precoding matrix (W2); wherein said step of reporting the secondprecoding matrix (W2) employs codebook sub-sampling; and wherein saidstep of reporting the second precoding matrix (W2) employs codebooksub-sampling as follows: W2 sub- sampling W2 sub-sampled codebook sizeRank 1 Rank 2 Rank 3 Rank 4 1-bit Y = e1 with (Y1, Y2) = Choose only Y =[e1 e5] only 2 out (e1, e1] 2 out of 16 with all 2 of 4 with all 2possible cophasing possible co-phasing (Y1, Y2), (Note this co-phasing(Note this e.g. (e1, [e1 corresponds (e.g. BPSK corresponds e5]) or([e1to i2 = 0, 1) only +/−1) to i2 = 0, 1) e5], e5) (Note this (Note thiscorresponds corresponds to i2 = 0, 2) to i2 = 0, 2) 2-bit Y = e1 with(Y1, Y2) = Choose only Y = [e1 e5] or all 4 (e1, e1] 4 out of 16 [e3 e7]with co-phasing or (e3, e3] possible all 2 (Note this with all 2 (Y1,Y2), co-phasing corresponds co-phasing e.g. (e1, [e1 (Note this to i2 =0, 1, (Note this e5]), corresponds 2, 3) corresponds (e3, [e3 to i2 = 0,1, to i2 = 0, 1, e7]), ([e1 4, 5) 4, 5) e5], e5), or ([e3 e7], e7) (Notethis corresponds to i2 = 0, 2, 8, 10) 3-bit Y = e1 or e3 (Y1, Y2) =Choose only No with all 4 (e1, e1] 8 out of 16 sub-sampling co-phasingor (e2, e2], possible (full set) (Note this (e3, e3], or (Y1, Y2),corresponds (e4, e4] e.g. the to i2 = 0-3 with all 2 even indexed and8-11) co-phasing or the last 8 (Note this (Note this correspondscorresponds to to i2 = 0-7) i2 = 0, 2, . . . 14, or i2 = 8-15) 4-bit NoNo sub- No n/a. sub-sampling sampling sub-sampling (full set) (full set)(full set)


20. A method of channel state information (CSI) feedback forcommunication between a base station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipment reportingvia a Physical Uplink Shared Channel (PUSCH) a CSI feedback signalincluding a rank indicator (RI) and at least one of the set including achannel quality indicator (CQI), a first precoding matrix (W1) and asecond precoding matrix (W2); wherein said step of reporting the secondprecoding matrix (W2) employs codebook sub-sampling; and wherein saidstep reporting the second precoding matrix (W2) employs codebooksub-sampling as follows: W2 sub- Example 1 Example 2 Example 3 Example 4sampling size Rank 3 Rank 3 Rank 3 Rank 3 1-bit Choose only Choose onlyChoose only Choose only 2 out of 16 2 out of 16 2 out of 16 2 out of 16possible possible possible possible (Y1, Y2), (Y1, Y2), (Y1, Y2), (Y1,Y2), e.g. (e1, [e1 e.g. (e1, [e1 e.g. (e1, [e1 e.g. (e1, [e1 e5]) or([e1 e5]) or ([e5 e5]) or ([e1 e5]) or ([e5 e5], e5) e1], e1) e5], e5)e1], e1) (Note this (Note this (Note this (Note this correspondscorresponds corresponds corresponds to i2 = 0, 2) to i2 = 0, 3) to i2 =0, 2) to i2 = 0, 3) 2-bit Choose only Choose only Choose only Chooseonly 4 out of 16 4 out of 16 4 out of 16 4 out of 16 possible possiblepossible possible (Y1, Y2), (Y1, Y2), (Y1, Y2), (Y1, Y2), e.g. (e1, [e1e.g. (e1, [e1 e.g. (e1, [e1 e.g. (e1, [e1 e5]), e5]), e5]), e5]), (e3,[e3 (e3, [e3 (e3, [e3 (e3, [e3 e7]), ([e1 e7]), ([e5 e7]), ([e1 e7]),([e5 e5], e5), or e1], e1), or e5], e5), or e1], e1), or ([e3 e7], e7)([e7 e3], e3) ([e3 e7], e7) ([e7 e3], e3) (Note this (Note this (Notethis (Note this corresponds corresponds corresponds corresponds to i2 =0, 2, to i2 = 0, 3, to i2 = 0, 2, to i2 = 0, 3, 8, 10) 8, 11) 8, 10) 8,11) 3-bit Choose 8 out Choose 8 out Choose only Choose only of 16 of 168 out of 16 8 out of 16 possible possible possible possible (Y1, Y2),(Y1, Y2), (Y1, Y2), (Y1, Y2), e.g. even e.g. even e.g. the e.g. theindexed indexed even indexed even indexed entries from entries from(Note this (Note this the codebook the codebook corresponds corresponds(Note this (Note this to i2 = 0, to i2 = 0, corresponds corresponds 2, .. . 14 2, . . . 14 to i2 = 0, 1, to i2 = 0, 1, 2, 3, 8, 9, 2, 3, 8, 9,10, 11) 10, 11) 4-bit No No No No sub-sampling sub-sampling sub-samplingsub-sampling (full set) (full set) (full set) (full set).


21. A method of channel state information (CSI) feedback forcommunication between a base station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipment reportingvia a Physical Uplink Shared Channel (PUSCH) a CSI feedback signalincluding a rank indicator (RI) and at least one of the set including achannel quality indicator (CQI), a first precoding matrix (W1) and asecond precoding matrix (W2); wherein said step of reporting secondprecoding matrix (W2) employs codebook sub-sampling; and wherein saidstep of reporting the second precoding matrix (W2) employs codebooksub-sampling as follows: RI Chosen W2 index for sub-sampling 1 Y = e1with all 4 possible co-phasing 2 Choose only (Y1, Y2) = (e1, e1) withall 2 possible co-phasing 3 Choose only 4 out of 16 possible (Y1, Y2),e.g. every 4th entry 4 [Y1 Y2] = [e1, e5] and [e3 e7] 5 All 6 All 7 All8 All.


22. A method of channel state information (CSI) feedback forcommunication between a base station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipment reportingvia a Physical Uplink Shared Channel (PUSCH) a CSI feedback signalincluding a rank indicator (RI) and at least one of the set including achannel quality indicator (CQI), a first precoding matrix (W1) and asecond precoding matrix (W2); wherein said step of reporting the secondprecoding matrix (W2) employs codebook sub-sampling; and wherein saidstep of reporting the second precoding matrix (W2) employs codebooksub-sampling as follows: RI Chosen W2 index for sub-sampling 1 Y = e1and e3 with all 4 possible co-phasing 2 Choose only (Y1, Y2) = (e1, e1)with all 2 possible co-phasing 3 Choose only 8 out of 16 possible (Y1,Y2), e.g. the even indexed or the last 8 4 All 5 All 6 All 7 All 8 All.


23. A method of channel state information (CSI) feedback forcommunication between a be station (eNB) and a plurality of userequipment (UE), comprising the steps of: each user equipment reportingvia a Physical Uplink Shared Channel (PUSCH) a CSI feedback signalincluding a rank indicator (RI) and at least one of the set including achannel quality indicator (CQI), a first precoding matrix (W1) and asecond precoding matrix (W2); wherein said step of reporting the secondprecoding matrix (W2) employs codebook sub-sampling; and wherein saidstep of reporting the second precoding matrix (W2) employs codebooksub-sampling as follows: RI Chosen W2 index for sub-sampling 1 Y = e1and e3 with all 4 possible co-phasing 2 Choose only (Y1, Y2) = (e1, e1)or (e3, e3) with all 2 co-phasing 3 Choose only 4 out of 16 possible(Y1, Y2), e.g. every 4th entry 4 [Y1 Y2] = [e1, e5] and [e3 e7] 5 All 6All 7 All 8 All.